Design of side Core-pulling Mechanism of Tilted Lifter
Shallow side concave of plastic parts requires small core-pulling distance, yet when the molding area of side concave is large, a large core-pulling force is thereby needed; therefore, titled lifter mechanism can be adopted for side parting and core-pulling. The characteristic is that the pushing force of the ejector is applied to drive the sideways movement of the titled lifter, and that the sideway parting and core-pulling action is completed by the titled lifter along with the ejecting and stripping of plastic parts. As indicated in Fig.2-17, the gist of design is as follows:
(1) For inner side core-pulling, top of the titled slide should be 0.05~0.1mm lower than the end plate of core, since during the protruding, the tilted lifter performs core-pulling action which moves inner side. To prevent the radial interference from bottom of the plastic part on core-pulling, the side bottom must be higher than the top of the mechanism, and meanwhile, opposite to the moving range S of the radial around the mechanism there must be provided with a S1 which is larger than the distance of S so that such barrier as circular bead can from to avoid interference on core-pulling, i.e. S1＞S.
(2) The pin’s dip angle β should be taken between 5°~25°, and the guide angle α on the core-pulling part of the mechanism should be smaller than or equal to β, i.e. α≤β.This id also for preventing the interference between the titled lifter and the bevel of core during the protruding.
(3) To endow the mechanism with restoration function, the length of circular bead for restoration should be adopted preferably larger under possible conditions, and the four corners of the side slide should be made into circular angles which are easy for mill processing. Such design shall ensure the steady and reliable restoration of the mechanism and meanwhile can also enlarge the space for processing.
(4) When slide friction between the titled lifter and the retainer plate of the ejector plate occurs, harden quenching should be applied to the head of the mandril and the insert of the roof plate to increase abrasion resistance.
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